Heat-controlled liquid switch



June 30, H. Loos HEAT-CONTROLLED LIQUID SWITCH Filed Oct. 10, 1951 f v aINVENTOR HERMANN L'OOSLI BY u /4K r'r"( Patented June 30, y 1953 UNITEDs'mrss PATENT OFFICE nsAr-conraotii n i ziduib SWITCH ApplicationOctober 10, 1951, Serial No. 250,641 In Switzerland February 9, 1951 3Claims.

My invention relates to thermally-operated liquid-containing switchesfor the control -of electric circuits, and preferably to mercuryswitches, which have a U-shaped envelope in whose limbs the mercury orother conductive liquid is driven back and forth by the alternateheating and cooling of a gaseous atmosphere enclosed in the limbs abovethe liquid, thus alternately closing and opening the electric circuitsof the gas heating means as well as the circuit proper to be controlled.

In the known switches of this kind, the electrio switching occursbetween a contact pin in each of the respective limbs of the U-shapedenvelope and the reciprocating conductive column of liquid. Withcurrents above a certain magnitude, depending among other things uponthe thickness of the contact pins, the current closing performance isnot immediately completed. When the contact pins are first touched bythe ascending conductive liquid, a temporary sparking occurs, similar tothat of a Wehnelt interrupter, resulting in high-frequency oscillations.Only when the contact pin more deeply sub merges in the rising liquiddoes the sparking cease, then completing the electric contactengagement.

From some applications, such as the control of blink lights, thesparking at the switch contacts is not detrimental to the operationproper, although it may then be necessary to provide suitable means forsuppressing radio interference in the vicinity. However, for otherpurposes, for instance when using the switch for the control ofcondenser discharges, the occurrence of sparking is a direct detrimentto the desired operation because the condenser discharge is oftenterminated before the electric contact engagement between the fixedelectrode and the liquid is perfected. During the sparking interval, thevoltage drop at the contact is relatively large so that a considerableportion of the discharge energy is wasted.

It is an object of my invention to obviate this deficiency and toprovide a liquid switch, generally of the above-mentioned type, that isvir=- tually or completely free of sparking tendencies.

To this end, and in accordance with my invention, I provide thesubstantially U-shaped switch envelope, containing mercury or otherconductive liquid, with two trap or overflow containers at the upperends of the respective envelope limbs so that the liquid column, whenbeing shifted by heat-responsive gas expansion from one limb to theother, will run into the container of the other limb to merge with theamount of liquid trapped therein, thus closing the electric circuit 2 bycontact engagement between two quantities of iquid;

These and more specific features of my invention will be apparent fromthe embodiment exemplified by the switch schematically illustrated onthe drawing in conjunction with an example of a capacitor circuit to becontrolled by the ic The illustrated switch has a sealed, substantiallyU-shaped vessel or envelope I, for instance of glass. The envelope iscomposed essentially of two bulbous containers or head portions 2a, 2band a U shaped tubular connecting portion 3. The connecting portion 3 isjoined With the head portions at their respective bottoms and forms acommunication between them. In the illustrated operative position of theswitch, the connecting portion 3 is substantially filled with conductiveliquid, for instance, mercury. The tube ends enter upwardly to someextent, for instance a few millimeters, into the space of each headportion 2a, 212 so as to form an annular trap space 4a or 41). Theliquid collected in these trap spaces is electrically insulated from theliquid column in tube 3 by the insulating tube wall. Two sealedinelectrodes 5a and 5b traverse the wall of the respective head portions2a and 2b and are contacted by the trapped amounts of liquid. Anotherelectrode 1 traverses the Wall of the tubular connectingportion 3 and isin contact with the column of liquid contained therein.

Each head portion 2a and 2b is equipped with an electric heater 8a or822. The upper ends or terminal wires of these heaters are sealedthrough the Walls of the respective head portions 2a and 2b. The lowerterminal wires to and 6b of the respective heaters terminate near theends of the connecting tube 3. The terminal piece Ea 1s sufiicientlylong to dip into the liquid column of tube 3 when the switch is not inoperation, while the terminal wire to is shorter and normany out ofcontact with the liquid column.

The space above the liquid within the head portions "2d and 2b ispreferably filled with hydrogen although another gaseous atmosphere maybe used instead. As mentioned, mercury is preferably provided as aconductive liquid but it will be understood that other conductiveliquids are also applicable.

The device is shown to be connected to a control circuit which includesterminals 9 for connection to a source of heating current for devices 8aand 8b, and a switch for placing the device in and out of operation.

Also shown is a capacitor charging and discharging circuit to becontrolled by the device.

The latter circuit has a capacitor l l, a schematically representedcurrent source l2, two resistors l3 and I4 that determine the timeconstants of the charging and discharging performance, and terminals [5at which the capacitor ll may be connected to some other apparatus inwhich its periodic change in condition is to be utilized.

The device operates as follows. Immediately after closing of the switch10, the current from the source connected to terminals 9 flows at firstthrough the heater Ba in head portion 2a, the pertaining contact wire Gaand the liquid column of tube 3 to the electrode 1, and thence back tothe current source. The gas within head portion 2a is heated andexpands. This forces the liquid column in tube 3 into the head portion21). As a result, the electric contact between the liquid column. andcontact wire 6a is interrupted so that the heater 8a becomesdeenergized. As the conductive liquid in the left-hand portion of tube 3rises sufliciently, it contacts the wire 6b and also overflows the tubeend, thus merging with the amount of liquid in the annular space ib. Asa result, an electric circuit is closed between the terminals and 5b.The energization of heater has the effect of forcing the conductiveliquid back through tube 3 into the head portion 2a so that the circuitbetween electrodes 1 and 51) becomes interrupted while a circuit is nowclosed between electrodes '1 and 5a. This operation is repeated as longas the switch remains closed. Each time the rising liquid in theconnecting tube portion 3 overflows into the trap space of the adjacenthead portion, it closes one of the two circuits available for control bythe device. The number of alternating closing operations per second canbe influenced 'by various means, for instance, by properly dimensioningthe length of the tube portion 3.

Due to the absence of spark discharges at the contact closing moments,the above-described device may be used, for instance, for thepractically loss-free chargin and discharging of capacitors. Thus, inthe illustrated capacitor circuit the charging of capacitor 1 I occurswhen the conductive liquid flows into the trap space 4?) thus closingthe circuit between electrodes 51) and 1, while the discharge of thecapacitor occurs when the liquid flows into the space 4a andinterconnects the terminals a and T.

It will be obvious to those skilled in the art that a switch accordingto my invention may be modified in various ways, especially as regardsthe materials used for the envelope structure and the specific shapegiven thereto, without departure from the essential features of myinvention and within the scope of the claims annexed hereto.

I claim:

1. A. heat'controlled electric switch, comprising a substantiallyU-shaped envelope having a bight portion and two limbs and having twohead portions forming respective overflow chambers at the respectiveends of said two limbs, a quantity of conductive liquid enclosed in saidenvelope and a gaseous medium above said liquid in each of said limbs,two electric heaters disposed in said respective head portions, each ofsaid heaters having a first terminal extending to the outside of saidenvelope and a second terminal disposed at the end of the pertaininglimb and engageable by the liquid contained in said bight portion andlimbs, an exteriorly accessible contact member mounted on said bightportion in contact with the liquid contained in said bight portion andlimbs,

and two contact members mounted on said envelope in said two overflowchambers respectively for engagement only by liquid collected in saidrespective chambers.

2. A heat-controlled liquid-containing electric switch, comprising asealed and insulating, substantially U-shaped envelope structure havingtwo containers and having a tubular connecting portion extendingdownwardly from said containers and forming a communication betweenthem, said portion extending upwardly into each of said containers andforming therewith an annular trap space at the container bottom, aquantity of conductive liquid normally disposed in said annular trapspaces and in said connecting portion, a gaseous medium enclosed in saidenvelope structure above said liquid, respective contact meansengageable by said liquid in said con necting portion and in saidannular trap spaces, two alternately operable heating means joined withsaid respective containers for heating said gaseous medium in eithercontainer to thereby displace the liquid in said portion into mergerwith the liquid in said annular trap space of the other container, eachof said heating means having a terminal electrode disposed in one ofsaid respective containers substantially in the center of said annularspace and extending downwardly to below the respective upper ends ofsaid connecting portion so as to be engageable by the liquid in saidconnecting portion before said liquid merges with that in the respectivetrap spaces.

3. A heat-controlled electric switch, comprising a sealed andsubstantially U-shaped envelope having a bight portion and two limbportions extending upwardly from said bight portion, said envelopehaving two head portions adjacent to the upper ends of said respectivelimb portions and communicating with each other through said bightportion, each limb portion having an overflow rim in the adjacent headportion and forming with said head portion a trap space for liquid, aquantity of liquid disposed in said trap spaces and in said bightportion when said envelope is in normal position, three mutuallyinsulated contact members disposed respectively in said two trap spacesand in said bight portion and being engageable by said liquid, a gaseousmedium disposed in said envelope above said liquid, two electric heatersdisposed in said respective head portions, each of said heaters havingtwo terminals of which one is disposed above the pertaining limb portionand engageable by said liquid in said limb portion when said liquidrises up to a given height near said overflow rim, a heating circuitconnected to said other terminals of said heaters and to said contactmember disposed in said bight portion, whereby said heaters when inoperation are alternately effective to cause said gaseous medium ineither head portion to displace the liquid in said bight portion towardcontact engagement with the liquid in said trap space of the other headportion.

HERMANN LOOSLI.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,124,625 Mishelevich July 26, 1938 FOREIGN PATENTS NumberCountry Date 383,687 Germany Oct. 16, 1923

